Ethylene and Sulfur Coordinately Modulate the Antioxidant System and ABA Accumulation in Mustard Plants under Salt Stress

Mehar Fatma; Noushina Iqbal; Harsha Gautam; Zebus Sehar; Adriano Sofo; Ilaria D'Ippolito; Nafees A Khan

doi:10.3390/plants10010180

Ethylene and Sulfur Coordinately Modulate the Antioxidant System and ABA Accumulation in Mustard Plants under Salt Stress

Plants (Basel). 2021 Jan 19;10(1):180. doi: 10.3390/plants10010180.

Authors

Mehar Fatma¹, Noushina Iqbal², Harsha Gautam¹, Zebus Sehar¹, Adriano Sofo³, Ilaria D'Ippolito³, Nafees A Khan¹

Affiliations

¹ Plant Physiology and Biochemistry Laboratory, Department of Botany, Aligarh Muslim University, Aligarh 202002, India.
² Department of Botany, Jamia Hamdard, New Delhi 110062, India.
³ Department of European and Mediterranean Cultures: Architecture, Environment and Cultural Heritage (DiCEM), University of Basilicata, Via Lanera, 20, 75100 Matera, Italy.

Abstract

This study explored the interactive effect of ethephon (2-chloroethyl phosphonic acid; an ethylene source) and sulfur (S) in regulating the antioxidant system and ABA content and in maintaining stomatal responses, chloroplast structure, and photosynthetic performance of mustard plants (Brassica juncea L. Czern.) grown under 100 mM NaCl stress. The treatment of ethephon (200 µL L^-1) and S (200 mg S kg^-1 soil) together markedly improved the activity of enzymatic and non-enzymatic components of the ascorbate-glutathione (AsA-GSH) cycle, resulting in declined oxidative stress through lesser content of sodium (Na⁺) ion and hydrogen peroxide (H₂O₂) in salt-stressed plants_. These changes promoted the development of chloroplast thylakoids and photosynthetic performance under salt stress. Ethephon + S also reduced abscisic acid (ABA) accumulation in guard cell, leading to maximal stomatal conductance under salt stress. The inhibition of ethylene action by norbornadiene (NBD) in salt- plus non-stressed treated plants increased ABA and H₂O₂ contents, and reduced stomatal opening, suggesting the involvement of ethephon and S in regulating stomatal conductance. These findings suggest that ethephon and S modulate antioxidant system and ABA accumulation in guard cells, controlling stomatal conductance, and the structure and efficiency of the photosynthetic apparatus in plants under salt stress.

Keywords: antioxidant; ascorbate-glutathione; ethylene; photosynthesis; salt stress; sulfur.